USB Flash Drives

Just wondering if anyone out there can help me. We've recently installed some new computers at our store and now our end of day backup is done to USB Flash Drive (or portable hard drive, probably not as convenient to carry back and forth). Overall, the backup time has been halved with the new server, but when it gets to the point of writing to the UFD, it seems to slow down considerably. Our IT guy who flew out from WA to install the new system says the total file its backing up is about 200MB, so he recommends a 4GB UFD to give it a few weeks worth before it rewrites over old news. At the moment we're using an Amicroe brand UFD and it probably takes 3 or 4 minutes to write to it. Some of the Sandisk and Kingston brand UFD's I've researched have a quoted write speed of 20MB/s or thereabouts. I'm assuming that means mega-bytes per second not mega-bits per second? If it was 20 mega-bytes per second, by my maths it should only take 10 seconds to write a 200 mega-byte file. Is there any other brand or solution that anyone can suggest? 3 or 4 minutes at the end of the day if not necessary is not good! Especially on a Friday! 
